The present invention relates to a system and method for delivery of a fluid to a patient, and more particularly, to an infusion set for a fluid pump that may be used, for example, to deliver insulin to a patient.
Currently, there are two primary methods of treating diabetes. One method involves taking multiple injections of long acting insulin on a daily basis. The second method is by continuous delivery of short acting insulin to more closely emulate the human pancreas. This may be accomplished using a syringe pump.
A syringe pump typically includes four major components. These components are a microprocessor controlled syringe pump, an insulin filled syringe, a hub and tubing set, and a cannula.
A syringe pump is often worn in a carrying case on a patient's belt, in a manner similar to a pager, or in more discrete locations such as a pocket or a brassiere. The syringe is mounted in the syringe pump and may hold enough insulin for three days. The hub serves as an interface between the syringe and a tubing set. At the end of a tubing set is a cannula typically made of either steel or Teflon. The cannula may advantageously be carried in a cannula assembly. The cannula assembly typically attaches to the patient by adhesive and is placed near the abdomen around and to the side of the navel. The cannula is inserted in fatty tissue and the insulin is injected subcutaneously.
A patient may perform activities that do not permit or are hindered by the presence of a pump, for example, when a patient wishes to take a shower or participate in certain athletic activities. Removing each of the components, including the cannula, would require a needle stick upon reconnecting the system to a patient. Since a needle stick is undesirable every time one wishes to take a shower or participate in sports, state of the art tubing sets disconnect at or near the cannula assembly, with the tubing capped to prevent contamination. Disconnecting and reconnecting the tubing set is sometimes difficult.
Cannulas with steel subcutaneous needles have been used with syringe pumps for decades. Steel needles, however, can cause irritation and discomfort. Soft cannulas, which may be made of Teflon, for example, help prevent this discomfort and are generally known in the art. The soft cannula requires the use of a steel insertion needle to penetrate skin and/or other tissue. When inserting the needle, the needle penetrates a first self-sealing septum in the cannula housing. The needle is then pushed through the soft cannula until it extends through the cannula's outer tip. After insertion of the needle into the skin, the steel needle is removed and the first septum seals the opening where the insertion needle entered. The tubing set may then be connected to the cannula by inserting a tubing needle at the end of the tubing set into a second septum in the cannula housing.
After removing the insertion needle, the first septum may be susceptible to leakage. This leakage may become more prevalent under pressure, such as when the cannula has an occlusion. Normally during an occlusion, the pressure will reach a threshold and trigger an alarm on the pump. However, if the first septum leaks, the pressure may never reach the threshold, and the pump may continue to deliver insulin. As a result, the insulin will continue to leak out of the first septum, the alarm will never trigger, and the user unknowingly does not receive the drug for an indefinite period of time.